1. Field of the Invention.
This invention relates to apparatus and method for the particularly thorough, non-invasive mixing of materials through vibration of the means in which said materials are contained, or through which said materials are flowing. More specifically, the invention relates to such apparatus and method as are particularly suitable for the mixing of fluid samples and reagents therefor in automated fluid sample analysis systems wherein the sample-reagent container is a reaction vessel, or a conduit of a continuous flow, automated fluid analysis system through which the sample and reagent are flowing.
2. Description of the Prior Art.
A wide variety of non-invasive mixing apparatus and methods are known in the prior art. These include static mixing appatatus and methods such as embodied by mixing coils or the like as commonly used in continuous flow sample analysis systems; and dynamic mixing apparatus and methods such as embodied in various agitator devices which vibrate, vortex or otherwise vigorously move a container for the purposes of mixing the materials contained therein. Non-invasive mixing apparatus and methods, of course, have the advantage of not introducing mixing blades or like mechanical devices into direct contact with the materials to be mixed, thereby avoiding potential contamination of those materials by the blades, and/or from one material to another.
More specifically, U.S. Pat. No. 3,844,067 to Borg discloses a magnetic vibrator for emulsifying milk in distilled water in patent FIG. 3. Magnetic vibrator 25 comprises magnetic coil 26, spring member 28 and armature 27. Tube holder 30 is fixed to armature 27 and rigidly holds tube 31 in an upright position. When the vibrator coil 26 is energized, tube 31 is vibrated in response thereto and mixes fluids contained therein. This apparatus provides no means for modifying the frequency or amplitude of vibration in response to the mass of the fluids to be mixed. Thus, different volumes, and thus masses, of fluids to be mixed, will be mixed at different efficiencies.
U.S. Pat. No. 4,264,559 to Price discloses a mixing device for laboratory tests in which the contents of the mixing container 19 are vibrated by spring-like metal lengths 1a and 1b which are mounted on upright mount 3 of base 9. Coupling mass 16 and upright clamp prong 18 are clamped to the lengths 1a and 1b. After mixing container 19 has been clamped to prong 18, the metal lengths are plucked by hand to impart a pendulum-like vibration to the metal lengths and the clamped container for a brief mixing period. Thus, mixing is not continuous, and no means are provided to relate the frequency or amplitude of the applied vibrational energy to the mass of the liquids to be mixed.
U.S. Pat. No. 3,338,047 to Kueffer discloses a frequency regulator for tuning forks wherein the frequency of vibration of the tuning fork is adjusted by adjusting the magnetic flux in the air gaps between the tuning fork tines, and the ends of a magnetic coil used to drive the tuning fork through C-shaped magnets 11 and 12 which are mounted to the ends of the fork tines 13 and 14. The magnetic coil produces driving pulses in proper phase relationship to sustain the vibration of the tuning fork at a predetermined frequency, which is adjustable as above by changing the magnetic reluctance of the coil core, by shunting a part of the magnetic flux between the ends of the core, or by moving the core back and forth along its axis. This patent is directed strictly to a timepiece driving system, and is in no way related to vibrational mixing.
U.S. Pat. No. 3,421,309 to Bennett discloses a unitized tuning fork vibrator directed strictly to the drive of a timepiece; while U.S. Pat. No. 3,382,459 discloses an electromechanical resonator comprising a tuning fork which may be driven in either of the tuning fork or reed modes of vibration for use in relay, oscillator or filter applications, and having no disclosed application to vibrational mixing.
U.S. Pat. No. 3,159,384 to Davis discloses a generally conventional agitation mixer in which a test tube is supported and agitated for mixing the contents thereof; while U.S. Pat. No. 4,042,218 discloses a generally conventional vortex mixer wherein a cylinder is driven at its base in a circular motion at substantially constant angular velocity to mix the fluids in test tubes as inserted into the cylinder.
To summarize this description of the prior art, it will be noted that no prior art is known to applicant which automatically relates the frequency of vibrational mixing to the mass of the materials to be mixed, or which enables the holding of the amplitude of vibrational mixing at that frequency to a predetermined level, both of which combine to optimize mixing while minimizing the required energy input.